Nitroglycerins, whether in gelatin or liquid form were used for many years to facilitate explosive fracturing. It was placed in an uncased well bore and detonated. However, the obvious disadvantages of using Nitroglycerin, due to its instability, are numerous. It is extremely shock sensitive, and difficult to transport and handle. Therefore it could not be pumped or poured into the well bore, and thus it had to be carefully placed in the well. There is always the risk of premature detonation as well as collapsing the formation. It has been estimated that thousands of potentially productive wells were ruined by using Nitroglycerin.
To overcome the drawbacks of using Nitroglycerin, experimentation with other liquid explosives and slurry explosives (solid explosives suspended in water or oil) were conducted. It was falsely believed that these explosives could be pressurized into the formation and the resulting explosion would not only frac the formation but would create a large cavity that would allow the fluid in the formation to flow freely to the well bore cavern. In general, these explosives were not successful for reasons, including instability, segregation of constituents, detonation inconsistencies under pressurization, and vulnerability to dilution of the explosive by the fluids in the well bore.
The basic principle of creating a cavity in low permeable formations by using explosives was widely accepted by engineers throughout the oil industry. In the late 1950's experiments were conducted in wells in West Virginia where thousands of pounds of TNT were placed in the well bore and detonated. In 1964, proponents of explosive fracturing were quite seriously suggesting that Thermo-Nuclear devices could be placed in tight formations and detonated in order to create a very large cavity whereby many wells in a given field would be affected.
The postulations formulated concerning increasing explosive components to enhance the fracing process did not take into consideration the viscous and thermal effects of the sonic waves that are propagated. A large explosion is likely to do more harm than good in a given formation due to the shattering and fragmation that occurs.
In order to achieve the optimum results in explosive fracturing, it is imperative that the intregity of the formation is not substantially altered. This premise is actually the foundation of this Sonic Frac Process.